Posted
by
samzenpus
on Wednesday March 06, 2013 @09:01PM
from the guided-by-the-light dept.

sciencehabit writes "In 1592, a British ship sank near the island of Alderney in the English Channel carrying an odd piece of cargo: a small, angular crystal. Once it was brought back to land, a few European scientists began to suspect the mysterious object might be a calcite crystal, a powerful 'sunstone' referred to in Norse legends which they believe Vikings and other European seafarers used to navigate before the introduction of the magnetic compass. Now, after subjecting the object to a battery of mechanical and chemical tests, the team has determined that the Alderman crystal is indeed a calcite and, therefore, could have been the ship's optical compass. Today, similar calcite crystals are used by astronomers to analyze the atmospheres of exoplanets—perhaps setting the stage for a whole new age of exploration."

This interested the hell out of me, I'd never heard of it before. Wikipedia says it was used to find the sun on a cloudy day, which would indeed be very useful to navigators with no compasses.

I find the timing of this story rather interesting, because the History Channel's newest special miniseries Vikings just started up this past Sunday. In it, the main character reveals to his brother a sunstone that a wanderer had given him. He then proceeds to find the sun through the clouds for his brother, who did not believe that the stone would work.

I find the timing of this story rather interesting, because the History Channel's newest special miniseries Vikings...

I was about to say the same thing!

Oddly, it's the second reference from that series that I ran into today. The other is the Shield Maidens. I just hit a part in the book, "The Mongoliad: Book One" that mentions them. I had never heard of them before the series or the book. (yeah, it's not quite as coincidental timing-wise, since the book was released well before the series, but it was a surprising coincidence to me nonetheless)

Wikipedia says they can find the sun's azimuth even when the sun is below the horizon!

http://en.wikipedia.org/wiki/Sunstone

The name derives from sunstones believed to have been used for navigation in the Middle Ages because their optical properties allow the azimuth of the sun to be detected even when the sun is below the horizon, with an accuracy within a degree or so.[1][2]

The way this works is that the atmosphere polarizes the light from the sun, and that can be detected before the sun rises or after it sets. On an overcast day, the polarization can be detected as well, giving a way to determine the azimuth of the sun even when it can't be seen by eye.

Calcite is birefriigant, meaning that rays of different polarization pass through a single crystal with rhombic cleavage plans in two paths, which you can see. I would assume that two crystals attached by with different orie

Might be worth noting that the operation of the stone in the show is fairly different from the description on wikipedia. In the show they basically hold it up to the clouds and see the sun through it. In Wikipedia they describe having to adjust the angle the stone is held at to detect circles in the sky and use that to locate the sun. Whether they are equivalent descriptions I cannot say. When they demonstrated the stone on the show I guessed it was calcite and had something to do with the polarization

Like you I looked it up on Wikipedia and was confused. The Sunstone [wikipedia.org] article said it was feldspar, not calcite as in the post. Then I dug deeper and the Sunstone (medieval) [wikipedia.org] article says the original sunstone used for navigation was calcite like Iceland spar. I don't know if the feldspar version could be used for navigation or not.

BTW, we don't need the sunstones (feldspar version) here in Oregon, we just have a supply for those that do.

I hope that by "battery of mechanical and chemical tests", they meant "showed it to a geologist for five minutes". There are a number of minerals which can mimic calcite to the untrained eye, but they're easy for the specialist to distinguish.

No kidding. 1) it has a hardness of 3 on Mohs hardness scale, 2) it fizzes in acid, 3) it has 3 perfect non-90-degree (rhombohedral) mineral cleavages, etc. Five minutes? More like under one minute. Even the photo is enough to tell that's very probably calcite.

On the other hand, maybe they needed non-destructive tests, which would make it slightly trickier (hence 5 minutes).

Actually, according to the abstract, they were trying to determine what happened to the crystal while it sat on the seafloor. Alteration from 400+ years of contact with seawater (plus sand abrasion) changed the physical and optical properties somewhat.

Actually, a crystal's basic physical and optical properties do not change even when it is eroded: one unit cell of the crystal has all the determining characteristics that a macroscopic sample would have. Given, it takes some training to tell a rough diamond apart from quartz, but that's what mineralogists and material scientists are for. Oh and one more thing: if it was at least a little transparent, the most readily distinguishable characteristic of calcite is that it's birefringent (check: Wikipedia [wikipedia.org] if y

As it happens, I'm a geologist. There's a difference between alteration and erosion. What the article refers to is the exchange of calcium and magnesium between the crystal and seawater (ratios of Ca and Mg move towards equilibrium with the ocean chemistry). That kind of substitution does change your unit cell a bit; which will alter the properties slightly. It would still be calcite (which is ridiculously easy to identify, as you say); just not quite the same calcite it was before it was dunked.

Reading the summary, it sounds like the calcite had been altered to the point where it couldn't be used as a sunstone (cloudy and scratched). The tests were to determine if the crystal would have made a good sunstone prior to being soaked/abraded.

In a discussion I had with a friend the other day about how did Vikings navigate? Mostly poor weather (no star sightings) and very close to magnetic north pole (compass is useless), or they only traveled part of year when weather was not really bad. One story I heard is they used pressure as a means of navigation. Huh? don't ask me, that is what someone else said. But since that was 1000 years ago, that knowledge is lost so all we have is speculation. Interesting to consider What If... they continued further south and settled in sunny Florida?

In the book "From Vinland To Mars" published in 1970s it said many Scandinavian men were "landless sons" since first born son inherits the land, and there is not much farmable real estate in those areas. So these landless sons don't have much career opportunity except join the Viking Navy and plunder rest of Europe but there was also motivation to go west to find other places to settle.

In those times there was simply not enough land to give each son a piece of the family tracts of land, so yeah, venturing out to sea was basically their only option. It is however an astonishing testimony to their persistence and ability to withstand hardships that they landed on another continent. Having to go cross-continent in a modern flying machine isn't exactly my idea of a fun time, even with all my electronic gadgets - I can't imagine what it must be like to be on a wooden ship for a year or more, w

I don't think they went from Norway to Newfoundland. Instead they went Norway -> Orkneys -> Iceland -> Greenland -> Newfoundland. So while still an amazing achievement, it was more like one more hop, mostly west, so tracking the sun is useful for that. The vikings from Greenland that sailed down to L'Anse aux Meadows had already been sailing west from Greenland to trade with the natives (the Dorsets?) and just kept going further. L'Anse aux Meadows was a long way from Greenland and the Indians further south would have been tough to fight, given the population of Greenland was small. So you can see why they did not establish large settlements there. If word had gotten all the way back to Norway and the multiple hops were easier then perhaps more would have settled but it didn't look as attractive as it did for the rest of Europe 500 years later.

Even with the sunstone, I still wonder how it is actually used in navigation.

The sunstone obviously determines the direction of where the sun is located - which can basically be anywhere, particularly in summer in the arctic when the sun doesn't set. I know how to get my heading using the sun (unless it's too high above me, like around midday in summer as I'm a hair south of the Tropic of Cancer) and a watch - it basically relies on knowing where the sun is at that moment, and knowing the actual time.

I can't find an image for it now, but I have seen a primitive portable sundial disk. I have a modern version as a novelty.

If you know north, you can find the time and vice versa. Aha you say, how do you know the time? Well in a "primitive" society, people could develop a sense of what time in was. This could be refined by practicing with the sundisk on land.

In an earlier age, railway engineers were said to be able to guess the time to a few minutes and only checked their watches for the minute.

You can estimate the time without a watch easy to 30 minutes accuracy.So knowing where the sun is gives you a good clue to where south is... or east or west, depending on the time.I'm used to look at the sun and point out north to about 5 - 10 degrees accuracy instantly.

While you are strictly speaking correct.This is not what old school navigation was about. They only used the sun as compass ersatz.And this crystals are useful to find the suns position even under fog or clouds.

See it this way: I want to sail strictly west. My latitude is irrelevant if I'm confident that I reach greenland as long as my course is good enough. Drifting to far south or to far north is my main concern...

So now the vikings may have had a way to tell where the sun was, with rather high accuracy, without knowing the time that information is rather useless. So something is definitely missing there.

It's easy to tell when noon is from a sundial. And if you know the date and the elevation of the noon sun, you can tell your latitude. And if you know your latitude and the date, you can tell what time and what direction sunrise and sunset are. And if you know a few times, you can use an hourglass or something to

Up is fixed, even on a boat. You can always find noon with a sun dial. By analysis of the shadow cast by a peg (similar to a sundial) you can calculate if you've deviated from a course provided you know what time it is and have a reference position to check against. The vikings would have known what time it was at least once a day.

You just provided one simple solution yourself. A simpler one would be to construct your dial of wood and put it in a deep bowl of water. Assuming the bowl is held down it shifts with the boat but the surface of the water remains level. Which is essentially the same thing you do with a compass. It isn't just the rocking of a boat but the improbability that you are holding your hand level. This would be a problem on land as well. Up is still up on a boat.

Its worth noting that while we know the Vikings for their raiding and pillaging, they were in fact some of the most successful traders in Europe at the time. They were also very good and competent craftsmen.What we get is the Evil Vikings (tm) version as related by the Christian Church, from when they were (gasp) Pagans and not subject to the rule of that church. Once they had been forced at sword-point to convert to Christianity they became more acceptable. Not that old Norse religion was anything to be particularly happy about mind you. My point is that the Vikings sailed their ships around Europe down into the Mediterranean, conquered Russia (the Rus were effectively Norseman), served as the Imperial Bodyguard for the Byzantine Empire etc. They didn't just destroy and pillage - and most of the other peoples in Europe did a lot of the same thing anyways.The Sunstone is a neat idea if true though. I would have bet the Norse navigated mostly by the stars myself, and that they tended to stick to being within sight of land most of the time as most people did prior to the invention of modern navigation.

Vikings have a reputation for being "evil" because they luted,raped and pillaged large areas of the British Isles. Sure they might have done other smart things, but that does not detract from the fact that they where nasty pieces of work.

Invoking Godwin's Law the Nazi's had lots of wonderful technological stuff as well. They where however still evil bastards.

Well, according to letters we have found from the time, the rape part might have been convinient lie. The danes were taller and blonder than the british, and they bathed regularly and braided their hair and beards. They settled part of Brittain in what became known as Danelaw, and was considered a nuisance because they could seduce even married women. They were later subject to a genocide and wiped out in Brittain.

Well, according to letters we have found from the time, the rape part might have been convinient lie. The danes were taller and blonder than the british, and they bathed regularly and braided their hair and beards. They settled part of Brittain in what became known as Danelaw, and was considered a nuisance because they could seduce even married women

When I first saw the headline, I thought it was going to be a fossilized bioluminescent sunstone [wikispaces.com] from H [wikispaces.com]. Beam [wikipedia.org] Piper [gutenberg.org]'s Little [tvtropes.org] Fuzzy [wikipedia.org] series of science fiction stories.

Still, a fascinating read, albeit not one as exciting as if H. Beam Piper's fictional sunstones had been found to exist in real life.

Since there appears to be at least two markets for calcite crystals, Astronomers, and I would expect the re-enactment community, I wonder if there is a means of creating either the variety needed by astronomers, or people interested in re-enacting voyages of vikings or others.

I would suspect that creating them would be potentially less difficult than creating man-made diamonds, but I haven't checked.

The question about creating it is not about simply generating calcite, or calcium carbonate, but in generating usable sized high quality crystals. Much of the stuff I've encountered in nature that is large enough to hold has crystals that are growing in multiple directions, with none discreetly large enough to be useful for either use. I'm quite certain that there are larger crystals that would be workable, but I'm wondering if the cost to grow high quality crystals might be low enough to make this into a w

I've done a lot of sailing on the Great Lakes and Irish Sea and I can tell you that cold water often brings a kind of dense low fog. There are times when we can see the tops of masts and blue sky above but because the sun is often low at these latitudes, we can't see where the sun is. But sometimes the fog was so bright, I'd wear sun glasses and then I did notice that the zenith blue sky was polarized. What's more, the digital watch we used for sailing was an LCD watch-- which means it polarized display. And the display did darken noticeably when turned at certain angles, so the reflected sky polarization was also discernible. At the time I wondered whether it could be used as a practical form of navigation, but we had a compass. A few years later Loran-C became popular addition to the compass as and then GPS. But when I heard about the theory that an Iceland spar sunstone might have been used for navigation in the high arctic, I'd give it the nod of plausibility. No it isn't as good as a compass, unless you're above 70 degrees magnetic latitude. No it wouldn't work well under conditions of total cloud cover or rain, might not work at all. But I'm sure this kind of low fog is at least as common in the arctic as it is at my latitude and if I were lost without a compass, GPS, Loran-C on a foggy day, you'd better believe I'd break out the sunstone if I had one.

Which, as a man of world, you must know is the source of iocane powder. And because iocane comes from Australia, and Australia is entirely peopled with criminals, and criminals would try to fool wandering Vikings into thinking they could navigate with an iolite stone, we know we cannot trust this story they've put in front of us.

I imagine that was "magic" back in the day. Just a little Viking sorcery! I suppose the reverse of the rule is also true; any sufficiently antiquated "magic" must seem like technology. Imagine the wonder of the first person to notice this. Did they closely guard their secret? Did this knowledge give them an edge over their neighbors?

By the time you get to 1767 [google.com], we're definitely leaning more toward "technology" (Though I didn't see this particular one mentioned in said document.) The math and devices are pretty well understood and the methods are shared openly. I'm sure I could find earlier documents if I were inclined to dig around a bit. This one actually popped up on a search for... something else I was looking for. Needless to say, I immediately decided I wanted to be a member of the Order of the Commissioners of Longitude. If they let me in I promise I'll sit in the back and be very quiet...

All the science can't really make things stop being magic. The "energy" that all the pieces are made of and the "force" that binds them are no less magic simply because we've given them labels and made rules for predicting and manipulating them. Someone who knows the ways of magic is a wizard. It's kind of amusing if you think about it, the quickest to scorn a supposed wizard would be our scientists and engineers but if scientists and engineers aren't our wizards who is?The ancients derived their 10 sphere

There's some interesting history behind the Board of Longitude. It was formed in 1714 to judge prizes of up to £20,000 for a reliable method of determining longitude at sea (this was the scientific problem of the day, comparable to the modern search for a cure for cancer or theory of everything). In the early days, the board was flooded with crank proposals, and the commissioners' duties consisted of individually writing letters of rejection. When John 'Longitude' Harrison arrived in London in 1730 wi

I personally never knew the Vikings had this optical compass thing going, but I see interesting possible ties to the Polynesians.

I spent about 20 years in the jewelry industry and I learned that calcite, at one time, was often mistaken for Diamonds. Calcite deposits are what gives Diamond Head in Hawaii it's name. The calcite was mistaken for Diamonds.

I wonder what the possibilities are that Polynesians used "Sun Stone" compasses to help find their way around the Pacific?